The GNU FreeFont package is still using system* instead of invoke in its
install phase, and this is failing silently:

------
mkdir /gnu/store/1nfp73g3s15dhpqjrbfsihk7jrcbbl1p-font-gnu-freefont-20120503/share/doc/font-gnu-freefont-20120503
cp -a README AUTHORS CREDITS COPYING ChangeLog INSTALL  /gnu/store/1nfp73g3s15dhpqjrbfsihk7jrcbbl1p-font-gnu-freefont-20120503/share/doc/font-gnu-freefont-20120503
cp -a notes/usage.txt /gnu/store/1nfp73g3s15dhpqjrbfsihk7jrcbbl1p-font-gnu-freefont-20120503/share/doc/font-gnu-freefont-20120503/USAGE
cp -a notes/troubleshooting.txt /gnu/store/1nfp73g3s15dhpqjrbfsihk7jrcbbl1p-font-gnu-freefont-20120503/share/doc/font-gnu-freefont-20120503/TROUBLESHOOTING
tar czvf freefont-ttf-20200422.tar.gz freefont-20200422/
tar: freefont-20200422: Cannot stat: No such file or directory
tar: Exiting with failure status due to previous errors
make: *** [Makefile:64: ttftar] Error 2
phase `install' succeeded after 0.2 seconds
------

Notice that it is using the current date. It doesn't work to use the
Unix epoch or the version of the package: 20120503 (see attached).

We should figure out what this is trying to accomplish, fix it, and
switch to invoke.

The fonts are getting installed AFAICT.